If the concrete surface is scratched or varnished, you should restain it. So, can you restain concrete and how to do it?
You can restain concrete if the surface isn’t defective or filthy. However, if the old stain is filthy or damaged by moisture, you must remove the stain before reapplying a new one.
To restain concrete, you must sand the stained surface with fine-grit concrete sandpaper. Sanding will remove imperfections and bumps from the concrete surface, increasing the bonding between concrete and stain.
Also, if the concrete stain is sealed, you must remove the sealer before applying the new stain. That’s because the sealer will prevent the new coating of stain from sticking.
Restaining Colored Concrete
You can restain colored concrete, but you must use acid stain to get the best results. If you use regular stain on concrete, the stain won’t penetrate the old concrete stain. That’s because of the hard nature (texture) of the concrete.
Also, you must use the same (or similar) color to restain colored concrete. That’s because the new stain coating won’t penetrate the old coating, so the colors will mix. As a result, the finish will appear lighter than it is.
The finish will look unprofessional and unfinished if you use a dark-colored stain over a light-colored stain. You must apply 3-4 coats of stain to prevent the old stain color from bleeding through. And, applying 3-4 coats of stain isn’t recommended because the finish will become too thick (and turn sticky).
You must apply a primer or concrete paste to prevent the old stained concrete color from bleeding through the new stain color. The primer (or concrete paste) will act as a “bridge” between the two coats of stain and prevent bleed-through. However, for the best results, remove the old stain and then apply a new one.
How To Restain Concrete?
Before restaining concrete, here are a few things you need to know:
- If the existing stain is sealed, you must remove the sealer before restaining.
- Acid-stains work best on concrete.
- Sand the existing stain to allow the new stain to stick better.
- It’s better to remove damaged stains than staining over them.
- It’s better to use the same color as the existing stain.
Here are the tools you need:
- Concrete sandpaper
- A gallon of acid stain for concrete
- Paint thinner
- A degreaser or concrete cleaner
- A pair of gloves
- A paintbrush or spray gun
- An acrylic-based sealant
1. Clean and Degrease The Concrete
First, clean and remove grease, oils, and dirt from the existing concrete stain.
To clean concrete stain:
- Use rubbing alcohol, TSD, white spirits, or concrete clear.
- Apply the solvent over the concrete.
- Use a soft brush to scrub (remove) the dirt.
- Remove the solvent residue with warm water.
- Don’t use too much water because concrete will take longer to dry.
2. Sand The Existing Stain On The Concrete
Once the concrete is dry, sand it. Sanding exiting concrete stain will remove bumps and imperfections from the concrete and allow the new stain to stick better.
To sand concrete stains, use fine-grit concrete sandpaper.
If the concrete stain is sealed (has a topcoat), you must remove it before restaining it. That’s because the sealer will prevent the stain from penetrating the concrete and sticking. This leads to restaining failing and concrete stain turning sticky.
To remove the sealant from the stained concrete, use mineral spirits.
3. Apply Acid Stain
Once the concrete is sanded and has no sealer, you can apply a primer (or concrete paste). The primer will prevent the old stain from bleeding through and help the new stain from sticking better.
If you are changing the color of the stain, applying primer is necessary. However, priming is optional if you use the same color shade as the old stain.
Once the concrete is cleaned, sanded, has no sealer, and primed (optional), you can apply the acid stain. The acid stain will stick better than the regular stain. Apply 2-3 coats of acid stain to restain the concrete. Wait until the previous coat dries before applying a new coat of acid stain. It takes acid stain 5-24 hours to fully dry.
4. Seal The Stain (Optional)
To increase the durability of the concrete stain, seal it with a top coat. When dry, a sealer will produce a glossy moisture-resistant layer that protects the concrete stain from water, moisture, scratches, and damage.
However, a sealer can change the color shade of the stain. For example, if you use polyurethane, the stained concrete will appear lighter. But, if you use wax, the stained concrete will appear darker.
Staining Over Acid-Stained Concrete
You can’t stain over acid-stained concrete because the acid stain will prevent a new stain from sticking. Acid stains set (penetrate) into the concrete surface. When you apply the acid stain, the stain will etch and “eat” into the concrete material, and then the color will set inside the concrete.
So, if you apply a regular stain over acid-stained concrete, the stain won’t stick because it can’t penetrate the concrete surface. Since the regular stain can’t penetrate the concrete, the finish will turn sticky.
To stain over acid-stained concrete, you must apply a concrete primer or paste, or remove the acid stain before restaining. The concrete primer or paste will provide a smooth undercoat for the stain to stick to.
You can also try applying an acid stain of the same color as the existing acid stain. The new stain will look better if the colors are the same. You should only apply an acid or water-based stain over an acid stain. Never apply oil-based stain or sealant over acid stain.
Stained Concrete Lifespan
Concrete stains last between 18 months and 4 years on concrete. The short life span of concrete stains is because stains, by design, are not durable. Unlike paints, stains are designed for beauty and not for protection.
So, stain makes the concrete look better, but it won’t protect it. If the concrete is exposed to heavy usage, foot traffic, or water, the stain will start to wash off.
However, you can increase the durability and lifespan of concrete stains by sealing them. When you seal the stain, the sealant will dry to form a hard moisture-resistant film that protects the concrete stain.
On average, sealed stains last at least 6 years on concrete. Stains sealed with 2-part epoxy can last over 8 years on concrete.
You can restain concrete, but you must use the same type of concrete stain (and color) or use a primer. Also, if the concrete stain is sealed, you must remove the sealer before restaining the concrete.